Hm. Well, let me toss Classic Deadlands into the mix. This is a non-d20 game, the precursor to Savage Worlds. A lot more baroque than it's progeny...
Remember that this isn't a medieval fantasy game. It's "Weird West", and in the genre, you can expect that if someone with moderate levels of skill points a gun at you, if he gets lucky, you might end up dead when he pulls the trigger.
A typical revolver is perhaps the most common weapon around, and does 3d6 points of damage. The dice "explode" (roll again and add) on a 6, so there is no theoretical maximum damage from a single shot. The average roll on a d6 is 3.5. On an exploding d6, it is 4.2.
You take the damage, divide by the target's size (a 6 for man-sized things), dropping fractions. This gives you a number of wounds. So, an average shot will to 12.6 damage - two wounds.
Those wounds are applied to a hit location (one of your arms, one of your legs, your guts, or your head - if you weren't making a called shot, you roll on a chart). As you take wounds to *any* location, you start taking penalties to die rolls. If you take six wounds in a given location, that location is "maimed". A maimed arm or leg ceases to function. If you are maimed in the head or guts, you are dead.
Now, some caveats:
If you hit the head, you get 2 more dice of damage. If you hit the "gizzards" you get one extra die of damage. An average shot to the head does 3 wounds, and a good one can kill you outright.
PCs have "Fate chips" that can cancel wounds when they are taken, as if they never happened.
Any hit, even if it doesn't inflict wounds, also inflicts at least 1d6 "Wind" - this represents pain and short-term breathlessness, fatigue, shock. If you run out of wind, you don't die, but you're winded, and can't do anything effective until you catch your breath. A typical character has between 8 and 24 wind. So, while your wounds are piling up scattered across your body, your Wind is all going one place. So, it is quite possible for you to taken out of action by wind, even if you aren't all that hurt.
Oh, and non-magical healing is *slow*. It can take weeks to recover from a major wound.
The above are the rules for PCs. You can use them for major NPCs and monsters, but the rules suggest some simple ways to deal with "mooks".